It’s official, Pluto is no longer a planet, and my very excellent mother will just have to find something else to swim under…
Meeting in Prague over the past week, IAU members rejected a proposal to increase the number of planets to 12 by including Ceres, the largest known asteroid, which orbits between Mars and Jupiter; Charon, which has been considered Pluto’s moon; and 2003 UB313, an object nicknamed “Xena” that was discovered in 2005 orbiting far beyond Pluto.
Pluto is now considered a “dwarf planet” because it has an oblong orbit that overlaps with Neptune.
Ceres and Xena will also be considered dwarf planets. Charon is simply one of the “small solar system bodies.”
Lodge your objections here.
I think it is the only sensible conclusion. Pluto should never have been nominated a planet in the first place. It was mainly due to erroneous conclusions about its size that it originally made the cut, and now it has been relegated to its true status as less than a planet. Although I am in favour of ‘planetoid’ rather than ‘dwarf planet’.
“planetismal” is one I’ve read in SF.
“planetet” just sounds silly, and “planetling” isn’t much better.
I quite like “planetino” or “planetito”.
I’m a bit surprised as I thought the odds were against Pluto being booted from the planetary fraternity.
Depending on how long ago this was announced the new may have not reached Pluto. But don’t be suprised if Pluto goes on a bender once it finds out. The humiliation!
Shouldn’t that be “a planet of restricted growth” (PORG)?
“Dwarf planet” is pretty offensive isn’t it?
They might as well say “Short Arse planet” or “Little Person Planet”.
I know nothing about science, so I can only suggest that Pluto gets some therapy and moves on.
They got dwarf stars. Why not dwarf planets. I like planetoid, myself. Anyway. Thus the mysterious process of classification goes on. And in the end, a thing can only ever be one thing or another. Pluto is either a planet, or it ain’t. If it can be both or either, then clearly the definitions need updating. But while we debate away here on earth, Pluto – whatever it is – just goes on doing whatever it is that it does…
Cheers…
Tigtog, I agree, ‘Planetito’ is the way to go. And now for a song:
According to the new definition, our moon is a planet.
“Huh?” I can hear you gasp. “What about the requirement that the object orbit a star? Our moon orbits the Earth.”
Well, it’s not quite that simple. The Moon’s trajectory through space is one that is everywhere concave with respect to the Sun. That is, it is always accelerating towards the sun, never away from it. So the Sun exerts a greater force on the Moon than the Earth does. Things that are in orbit around the earth are always accelerating towards the earth, but sometimes away from the Sun.
So what we have is a double planet, not a planet and a satellite.
Sylvia.
Would argue that point Sylvia – of the newly codified three principles of correct planet living, the object must orbit its star, not another object & while there is a little technical issue as to whether it orbits or we spin, its position in relation to Earth & the star burning away over there, is maintained by our gravitional pull, in combination with the sun. Would go for moon on that basis , not planet.
How many astrologers dropped their crystal balls this morning? For those who haven’t yet discovered the delights of Ptolemy II’s column Starlite in the SMH Good Weekend – go & be amused. The difficulty is restraining oneself from ripping the paper open while still in the newsagent – hold out & then savour.
No, no, no. It has to be a Planette. Sort of like a celestial back-up singer to the rock gods of the solar system.
I vote for Christine’s suggestion.
A wee Planette.
I was going to do a kinda undergod/underdog type thing but nah doesn’t really do much for me.
Bernice
I wasn’t taking the Earth’s spin into consideration at all. It’s irrelevant to the question. The question cannot be resolved merely by arguing that the Moon path is determined by the combination of the Earth’s and Sun’s gravity. After all, the Earth’s path is determined by the combination of the Moon’s and Sun’s gravity. Nor can the question be resolved by the fact that the Earth’s grativity is larger than the Moon’s. If that were the criterion, then a genuine double planet, where one is only slightly larger than the other, would be classified as a planet and satellite, which is absurd.
If such a system were considered a double planet, but the Earth Moon system is considered a planet and satellite, then somewhere between them there would have to be an arbitrary line that separates double planets from planet satellite systems.
The stated criterion is that a planet orbits a star. I’m supposing that means that the trajectory constantly curves towards the star, and never away from it. On that basis, the moon is a planet, not a satellite.
That said, I suspect that with some double planet systems one would find that each sometimes curved away from the star, and such a system would be regarded as being a double satellite, which seems silly.
Maybe I’ll go back to my earlier position on this question, which is that it’s all angels on a pin-head stuff.
Sylvia, your definition of an orbit would only hold if it was perfectly circular, but most orbits are elliptical. Since an orbit involves a revolution around a central point, you could argue that the Moon also orbits the Sun as it goes along with the Earth. But its primary orbit is around the Earth.
This discussion has me in a spin.
So who’s going to write the Orbituary?
Fatfingers,
I do not see why my argument only works for circular orbits. I did not talk about the curvature having a constant magniture, only having a constant sign – ie, always towards the sun.
On doing some further searching, I’ve found indications that the definition excludes the Moon from being a planet because the common centre of gravity of the Earth Moon system lies within the Earth. Since the Moon is receding from the Earth due to tidal drag, one day it will be far enough away for the common centre of gravity to be above the surface of the Earth, at which point the Moon’s status would change.
The Moon would also be deemed a planet now if the Earth were rather denser, having the same mass, with the result that the surface would be below the common centre of gravity.
Like I said, it’s angels on pin-heads.
Sylvia.
TimT, the Orbituary has already been written by Eric Idle in The Galaxy Song. You just have to change the dedication from ‘Mrs Brown’ to ‘Mr Pluto’. See http://www.gecdsb.on.ca/d&g/astro/music/Galaxy_Song.html
What are people born under Scorpio going do without their ruler Pluto?
They really didnt think this through at all.
“oblong” orbit ?
And what of my memory poem thingy, taught to me by my mother: ‘men very easily make jam sandwiches using new preserves’. It won’t make sense without the preserves. And I’ve already taught it to my kids.
Well at least we’ll always have ‘Every Good Boy Deserves Favour’.
Until some crew of geniuses decides to tell us that ‘F’ isn’t really a ‘note.’
Look I don’t mind too much if Xena isn’t a planet. She should have had a matching Planette Gabrielle. Just sayin…
Neptune and Uranus give me the shits too.
Anything that can’t be seen with the naked eye from good ol’ Planet Earth shouldn’t qualify as a planet.
Neptune, Uranus and Pluto, and for that matter Xeno, Planet Spock and every other god-foresaken lump of irrelevance in the entire unperceived universe oughta be recategorised as cryptoplanets.
In any case: planet (from the Greek πλανήτης, planētēs, means “wanderer” or more forcefully “vagrant, tramp”.
So what’s so great about being a planet?
Thirdcat, just substitute ‘newts’ for ‘new’ and you don’t need ‘preserve’. Plus it’s funnier.
Sylvia said: “I did not talk about the curvature having a constant magniture, only having a constant sign – ie, always towards the sun.”
OK, I may be putting my foot in it now, but is ‘magniture’ actually a word? And what the hell is a ‘constant sign’ in this context?
The way I understand it, a circular orbit is constantly falling towards the centre, but going fast enough that the centre ‘falls away’ just as fast. In an elliptical orbit (ie all planets), as the body moves toward apogee it is in fact moving *away* from the sun before running out of momentum and then falling towards it, repeat ad nauseum.
“the definition excludes the Moon from being a planet because the common centre of gravity of the Earth Moon system lies within the Earth.”
OK, so you have joined the rest of us in agreeing that the Moon is not a planet? Good for you.
“One day it will be far enough away for the common centre of gravity to be above the surface of the Earth, at which point the Moon’s status would change.”
So what? As of right now, it is Earth’s satellite, not a planet.
PS No need to sign your posts.
Fatfingers
This was never about whether the moon is or is not a planet in any absolute sense, but about whether it is a planet within the IAU definition. A definition that leads to the status of an object varying with time leaves a lot to be desired.
Thanks for pointing out the blindingly obvious typo in “magniture”, which everyone no doubt realised should have been “magnitude”. “Constant sign” means “not varying sign”.
PS I’ll sign my posts if I feel like it, just as I’ll post using my real name because I feel like it instead of hiding behind a pseudonym.
Sylvia.
If it were up to me, I wouldâve let Pluto be a planet âjust becauseâ?. Something like, a planet is an object which:
in orbit around a star or stellar remnants;
has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape;
is not massive enough to initiate thermonuclear fusion of deuterium in its core; and,
has cleared the neighborhood around its orbit; or,
is Pluto.
We donât need a perfect definition of everything: Weâve managed to get by perfectly well without one of planet till now. Then again, Ceres, the Moon and the Sun have all once been planets but are no longer.
Incidentally Sylvia, Wikipediaâs article on planets says:
It doesnât say anything in particular about those systems (like Earth and the Moon) where the barycentre is beneath the surface of one body or the other, which makes me suspect theyâre not meant to be classified as planets: But unless this is a hidden part of the definition of âorbit around a star or stellar remnantsâ? (or maybe clearing the heighborhood), youâd think itâd need to be explicitly stated. (Also, maybe itâs relevant that like most other moonâs, ours always shows us the same face; but the Earth shows different faces to the Moon. But a quick google suggests that Charon and Pluto are both tidally locked to each other.) The astronomers who chose this definition probably have other assumptions that Iâm unaware of tho, not being an astronomer and all…
Perhaps thereâs something in the definition of ânatural satelliteâ? that answers this predicament. Perhaps in this definition frenzy, the terms ânatural satelliteâ? and âmoonâ? will earn themselves a definition too?
What a futile issue! Can anyone tell me in what physical respect Pluto has changed since last week that depends on what a tiny group of self-important academics classify it as?
whyisitso: “…Can anyone tell me in what physical respect Pluto has changed since last week…”
Why yes, I suppose I could tell you in great detail what has physically changed about Pluto in the past few weeks, if I thought your puny Earth brains could comprehend the science of invisible rays in the ninth dimension; but then again, if you just keep your telescopes trained on my planet, you’ll probably be able to see for yourselves in, oh, about one more Charonic deca-month — that is, if I can believe the promises of my Grand Vizier of Military Supertechnology.*
Those West Plutonian scum are in for the surprise of their miserable lives, I can safely say that much…
(* — and if he turns out to be wrong, well, at least the Ice Spiders will be in for quite a treat.)
Excuse me. Where I wrote above, “if I thought your puny Earth brains could comprehend…”
should read,
“if I thought your puny Earth mono-brains could comprehend…”
Cultural differences, and what-not.
Sylvia, how do I know your sig is your real name? How do you know my real name isn’t fatfingers? That is a pointless argument, done to death in the blogosphere. You must be a newbie. If I used my real name (OK, you got me, fatfingers is not it), it is unusual enough that you would probably believe it to still be a pseudonym. To make a long story short – it is my argument that matters, not my identity.
“A definition that leads to the status of an object varying with time leaves a lot to be desired.”
Oh, no! A celestial body that goes through various stages? What is the world coming to? Never mind those proto-stars that become stars that become brown or red dwarfs or black holes or supernovas – they don’t count. Forget those asteroids that are captured by a gravity well and become satellites. Ignore asteroids knocked out of orbit who become comets. The universe is static and all its components are stuck in their definitions, never to change.
It must be nice to live in the 17th century.
PS I still don’t know what ‘sign’ you’re talking about. Perhaps the zodiacal kind?
PPS Your post is automatically signed by filling in the Name field. Perhaps you were unaware of this fact, Ms Repetitive?
As has been pointed out elsewhere, call Pluto an asteriod and it’s gonna start behaving like one.
Never mind a freakout over personal entertainment and cosmetic products do we really want to piss off several billions of rock in an unstable (or least elliptical) orbit?
I for one am not prepared to entertain this risk to our way of life. Give Pluto a seat at the UN Security Council pronto. India can wait.
Fatfingers,
Seems I’ve touched a nerve.
As for my name being genuine, just do a search for it in Google. That should make the situation clear enough.
Sylvia.
Thanks Sylvia, I did as you suggested and I’d just like to thank you for the most thoroughly wierd but sastifyingly narky political conversation I’ve read in a very long time.
Liam,
I never did understand why this guy, who runs a nudist resort in tropical north Queensland, should have got such a bee in his bonnet about what I was doing in New South Wales.
I just ignore him.
Sylvia.
Sylvia
I think you should get a gravatar.
Thanks
Zoe
Kim, you will be very pleased to know that Xena does indeed have a companion nicknamed Gabrielle.
Unfortunately, these nicknames don’t meet the IAU’s guidelines for permanent planet names, so unfortunately the Warrior Princess and her very good friend will not have a permanent place in the heavens.
Sylvia, because I responded to your inanity, you have touched a nerve? You flatter yourself.
Search for ‘fatfingers’ and you’ll get lots of hits as well. My point stands – you could be anyone at all claiming to be Sylvia Else.